Spring contact element



Nov. 19, 1963 c. E. ROBINSON SPRING CONTACT ELEMENT Filed Nov. 30, 1960 INVENTOR. CHARLES E. ROBINSON BY Bunch ar-u;

ATTORNEYS United States Patent .0 'ce 3,111,568 SPRKNG (IQNTACT ELEMENT Charles E. liiohiuson Wolcott, Conn assignor to Anaconda American Brass (Iornpany, a corporation of Qonnecticut Filed Nov. 3t 1960, Ser. No. 72,764 iliaims. (Cl. 2tl0130) This invention relates to spring contact elements for use with electrical fixtures such as fuses and the like having circuit components and a screw-type base of dielectric material and, more particularly, to a novel spring contact element which is formed from an electrically conductive self-supporting Wire.

In electrical fixtures which have threaded base members of a dielectric material, it is generally necessary to provide an electrically conductive element which is connected to the circuit components of the fixture and is formed to make electrical contact with the socket element into which the fixture is adapted to be screwed. These elements, which are known as spring contact members, have ordinarily been stamped from sheet or strip metal and subsequently bent and folded into the desired shape. However, they are relatively expensive to manufacture in this manner due to the considerable amount of scrap loss entailed in the stamping operation. Owing to the peculiar configuration which these elements must possess to perform the function required of them, even the best designed patterns for stamping have been unsuccessful in avoiding appreciable waste of the sheet or strip material.

The present invention has as an object to provide a novel spring contact element which is relatively inexpensive to manufacture. This is accomplished by providing a new design which permits the elements to be formed by cutting successive lengths of self-supporting electrically conductive wire and working them into the desired shape. There is almost no scrap loss connected with this operation and the cost of manufacturing is thereby reduced considerably from that involved in stamping out conventional spring contacts. Furthermore, a more resilient and more durable element than the stamped elements is provided by forming the wire according to the present invention.

The spring contact element of the present invention is designed for use with an electrical fixture having circuit components and a screw-type base of dielectric material. The new element comprises a substantially C-shaped electrically conductive member formed from a length of selfsupporting wire. Connecting means are included on the C-shaped wire member for anchoring it to the dielectric base in electrical contact with the circuit components and at least one resilient portion is formed in the C-shaped member for making electrical contact with the socket element.

A preferred embodiment of the invention is described below with reference to the accompanying drawing, wherein FIG. 1 is an elevation partly in section of the new contact element on a fuse;

FIG. 2 is an enlarged bottom plan view of the contact element and fuse of FIG. 1;

PEG. 3 is a bottom plan view of the contact element above; and

FIG. 4 is an elevation of the new contact element.

As shown in FIG. 1, an electric fuse it? consists of a substantially cylindrical ceramic member 11 having an irregular bore extending axially therethrough and an externally threaded base portion 12 and a shoulder portion 13. The threaded base portion 1'2 is of smaller outside diameter than the shoulder port-ion l3 and is adapted to be screwed into an electrical socket element. A lower shoulder surface 1-;- is defined on the shoulder portion 13 sion of the contact member 18.

Patented Nov. 19, 1963 by the reduction in the diameter between the shoulder portion and the threaded base portion 12. A well 15 has an opening on the lower shoulder surface 14 and extends upwardly into the shoulder portion 13 for a substantial distance. A metallic strip 16 which is held in place by a deposit of hardenable filler material 17 forms the closed end of the well 15.

Disposed within the axial bore extending through the ceramic member 11 is a terminal member 18 having a head slightly larger than the bore opening at the end of the threaded base portion 12. Soldered to the contact member 18' is a helical connecting wire 19 which winds about a dielectric plug 26. The plug 20 is an axial exten- The helical wire 19 terminates at the end of the plug 20 and is securely attached thereto. The end of the helical contact wire 19 is softsoldered to the metal strip 16. A tension spring 22 is connected to the strip 16 at this soldered joint and the opposite end of the spring is suitably attached by a pin 23 to the top of the shoulder portion 13. The spring 22 tends to draw the strip 16 away from the wire 19 so that when current overloads the fuse the solder melts and the strip 16 is pulled out of contact with the wire 19. A transparent Window 24- rests on the top of the shoulder portion 13 and is held firmly in place by a cap 25 which is crimped around the shoulder portion.

As shown in FIGS. 3 and 4, a spring contact element 26 is formed of a self-supporting electrically conductive wire 27 having a substantially C-shape. In FIG. 2, it is shown disposed on the lower shoulder surface 114 of the ceramic member 11 substantially concentrically about the threaded base portion 12. Formed substantially equidistant from each end of the wire 27 is a U-shaped integral loop portion 2 3 which extends substantially normal to the plane of the C-shaped wire up into the well 1'5 and makes electrical contact with the strip 16. This loop portion may be wedged into place in the well 15, or cemented therein, or otherwise attached to insure that the contact element is securely anchored to the body of the fuse.

In this embodiment, the end portions of the wire 27 are bent to form arcuate sections 23 and 3%. As shown in FIG. 3 the arcuate sections 29 and 3t) are preferably flattened in order to make better electrical contact with the socket into which the fuse is adapted to be screwed and also to increase the resiliency of the wire at this point by the additional cold working step. When the contact member as is attached to the lower shoulder surface 14- in the manner shown in FIG. 2, the arcuate sections '29 and 3%) are in their undeformed position extending away from the shoulder surface for making contact with the socket into which the fuse 10 will be screwed.

It is characteristic of the new spring contact element 26 that its nominal cross sectional shape is circular, thereby permitting it to be formed from a short length of wire stock. Only the opposite end portions thereof depart from this shape, and they have a thin and relatively wide cross-sectional configuration which can be readily formed by flattening the wire stock. (This flattening step is beneficial because it additionally cold-works the wire at its arcuate sections 29 and 36* and thereby imparts comparatively more resiliency to those regions where the element is to be elastically depressed in operation.) Consequently, the spring contact elements of this invention can be made in a relative limited number of working steps performed on consecutive wire blanks which are cut from an indefinite length of stock. There is little, if any, scrap loss in an operation such as this.

A further advantage of making the new element from wire is that it is superior to strip stock in permitting the formation of the arcuate sections 29 and 30' and loop portion 28 at right angles to the C-shaped plane of the element. Strip cannot generally be stamped or worked severely in different directions out of its own plane, whereas wire stock has no plane and bends readily in all directions.

I claim:

1. For use with an electrical fixture having circuit components and a screw-type base of dielectric material adapted to be threaded into an electrically conductive socket element, a spring contact element comprising an electrically conductive substantially C-shaped member formed from a length of self-supporting wire having a generally circular cross section, connecting means on said C-shaped wire member for anchoring it to said dielectric base in electrical contact with said circuit components, and at least one resilient flattened portion formed in said C-shaped member and extending out of the plane of the C-shaped member for making electrical contact with said socket element.

2. For use with an electrical fixture having circuit components and a screw-type base of dielectric material adapted to be threaded into an electrically conductive socket element, a spring contact element comprising an electrically conductive substantially C-sliaped member formed from a length of self-supporting wire having a generally circular cross section, connecting means on said C-shaped Wire member for anchoring it to said dielectric base in electrical contact with said circuit components, and resilient arcuate flattened sections formed in the respective end portions of said C-shaped wire member and extending out of the plane of the C-shaped member for making electrical contact with said socket element.

3. For use with an electrical fixture having circuit components and a screw-type base of dielectric material adapted to be threaded into an electrically conductive socket element, a spring contact element comprising an electric-ally conductive substantially C-shaped member formed from a length of self-supporting wire having a generally circular cross section, an integral loop portion formed in said C-shaped wire member substantially centrally between the ends thereof for anchoring it to said dielectric base in electrical contact with said components, and resilient arcuate flattened sections formed in the respective end portions of said C-shaped wire member and extending in a direction opposite that of said loop portion for making electrical contact with said socket element.

4. In combination with an electrical fixture having circuit components and a screw-type base of dielectric material adapted tobe threaded into an electrically conductive socket element, a spring contact element comprising an electrically conductive substantially C--shaped member formed from a length of self-supporting :wire, a substantially U-shaped integral loop portion formed in said O- shaped member substantially centrally between the ends thereof, said loop portion extending substantially normal to the plane of said C-shaped member and being anchored to said dielectric base in electrical contact with said circuit components, and a pair of similar resilient arcuate flatened sections formed in the respective end portions of said C-shaped wire member extending in a direction opposite that of said loop portion for making electrical contact with said socket element.

5. in combination with an electrical fuse having interior circuit components, a screw-type base of dielectric material adapted to be threaded into an electrically conductive socket element, and a shoulder portion of dielectric material encircling said base, a spring contact element comprising an electrically conductive substantially C-shaped member formed from a length of self-supporting wire and arranged on said shoulder portion substantially concentrically about said scrcu base, a substantially U-shaped integral loop portion for-med in said C-shaped wire member substantially centrally between the ends thereof, said loop portion extending substantially normal to the plane of said C-shaped wire member and being securely embedded in said shoulder portion in electrical contact with said interior circuit components, and a pair of similar resilient arcuate flattened sections formed in the respective end portions of said C-shaped wire member on opposite sides of said base and extending away from said shoulder for making electrical contact with said socket element.

References Cited in the file of this patent UNITED STATES PATENTS 1,539,870 Sandin June 2, 1925 1,672,664 Van Amburg June 5, 1928 1,684,170 Clark Sept. 11, 192.8 2,311,019 Bayne Feb. 16, 1943 2,750,475 Olason June 12, 1956 2,890,316 Gienger et al a June 9, 1959 

1. FOR USE WITH AN ELECTRICAL FIXTURE HAVING CIRCUIT COMPONENTS AND A SCREW-TYPE BASE OF DIELECTRIC MATERIAL ADAPTED TO BE THREADED INTO AN ELECTRICALLY CONDUCTIVE SOCKET ELEMENT, A SPRING CONTACT ELEMENT COMPRISING AN ELECTRICALLY CONDUCTIVE SUBSTANTIALLY C-SHAPED MEMBER FORMED FROM A LENGTH OF SELF-SUPPORTING WIRE HAVING A GENERALLY CIRCULAR CROSS SECTION, CONNECTING MEANS ON SAID C-SHAPED WIRE MEMBER FOR ANCHORING IT TO SAID DIELECTRIC BASE IN ELECTRICAL CONTACT WITH SAID CIRCUIT COMPONENTS, AND AT LEAST ONE RESILIENT FLATTENED PORTION FORMED IN SAID C-SHAPED MEMBER AND EXTENDING OUT OF THE PLANE OF THE C-SHAPED MEMBER FOR MAKING ELECTRICAL CONTACT WITH SAID SOCKET ELEMENT. 